Infrared sensors compatible mainly with infrared rays in an 8 μm to 12 μm band are used for security cameras and in-vehicle forward-monitoring cameras, being highly sensitive to infrared rays emitted from objects with temperatures particularly close to room temperature. In recent years, as the MEMS (Micro-Electro-Mechanical System) process has developed, uncooled (thermal) infrared sensors are being more and more widely used to detect infrared rays, without cooling devices.
A thermal infrared sensor uses pixels that are arranged in an array on a semiconductor substrate and are thermally isolated from the semiconductor substrate, to absorb infrared rays gathered by a lens for far-infrared rays (a Ge lens in most cases). The thermal infrared sensor thermoelectrically converts the temperature rise occurring in the pixels into electrical signals, and reads the electrical signals. The thermal infrared sensor then forms an image based on the electrical signals. A thermal infrared sensor that has an interconnect layer simplified to lower the heat capacity of each cell and is capable of making quick responses has been suggested (see JP-A 2003-65842 (KOKAI), for example).
In the thermal infrared sensor disclosed in JP-A 2003-65842 (KOKAI), the heat capacity of each cell is lowered by simplifying the interconnect layer, so that quick responses can be made. In the thermal infrared sensor disclosed in JP-A 2003-65842 (KOKAI), however, the location of an object cannot be quickly and readily determined. Furthermore, since the thermal infrared sensor disclosed in JP-A 2003-65842 (KOKAI) is an image sensor, a scanning operation needs to be performed to read output signals by selectively scanning rows sequentially one by one, and such a scanning operation requires a longer time to read a larger number of rows. Therefore, the infrared response speed of the pixels cannot be advantageously utilized.